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How Many Amps is 50 Watts? – Calculation Guide

Written by Edwin Jones / Fact checked by Andrew Wright

how many amps is 50 watts

It is critical to understand the amp rating of any device, even low-powered ones, in order to keep both the device and the circuit safe. This is especially critical if you intend to install numerous low-wattage appliances or add them to existing circuits.

In this article, we will discuss how many amps is 50 watts using different formulas for various circuits. This way, even if you’re not a professional, you will know the current draw of small devices.

How Many Amps Do 50 Watts Have?

Knowing how much current electrical devices draw is essential when constructing a circuit or adding a new device to an existing one. Understanding the needs of low-powered devices can help prevent circuit overloads and other electrical problems.

Suppose you have a 50-watt light bulb. If you intend to install many light bulbs or other low-wattage devices, you must determine how much current each consumes. Fortunately, here’s a handy table that can help you determine how many amps a 50-watt item requires.

Phases  System Voltage  50 Watts to Amps (in Different Voltage Ratings) 
DC  12 Volts  4.16 Amps 
24 Volts  2.08 Amps 
AC Single Phase (PF = 1)  120 Volts  0.41 Amps 
240 Volts  0.21 Amps 
AC Three Phase 
(Line to Line Voltage) (PF = 1) 
480 Volts  0.060 Amps 
600 Volts  0.048 Amps 
AC Three Phase 
(Line to Neutral Voltage) (PF = 1) 
277 Volts  0.060 Amps 
347 Volts  0.048 Amps 

According to the chart, a 50-watt device on a 120-volt circuit will draw around 0.41 amps, while the same device on a 240V circuit will draw approximately 0.21 amps. With this information, you can guarantee that your circuit is properly configured to meet the electrical demands of your gadgets.

However, if you’re curious about how the conversion works, the guide below may be useful.

How to Calculate Using Amperage Calculator?

Depending on the phases of the electrical system, multiple formulas are required to calculate amps from watts. In this case, here are the formulas that can be applied to each step individually.

  • DC formula: \[
    \text{{Amps}} = \frac{{\text{{Watts}}}}{{\text{{Volts}}}}
  • AC single-phase formula: \[
    \text{{Amps}} = \frac{{\text{{Watts}}}}{{\text{{PF}} \times \text{{Volts}}}}
  • AC three-phase line-to-line voltage formula: \[
    \text{Amps} = \frac{\text{Watts}}{\sqrt{3} \times \text{PF} \times \text{Volts}}
  • AC three-phase line-to-neutral voltage formula: \[
    \text{Amps} = \frac{\text{Watts}}{3 \times \text{PF} \times \text{Volts}}

Some of the formulas to convert watts to amps include the power factor. This power factor refers to the device’s efficiency and is good to understand for a more accurate amperage calculation. An incandescent lamp, for example, has a power factor of 1.

In this example, let us use a 50-watt incandescent lamp with a power factor of 1 to calculate watts to amps in various electrical phases.

  • For DC

To calculate the amperage rating of 50 watts, you must be specific about the voltage in the circuit and use the equation above. For instance, if you want to use a 50-watt light bulb at 12V, the calculation will be as follows to get the total current draw:

50 watts divided by 12 volts is equal to 4.16 amps.

  • For AC Single-Phase

In a single-phase electrical connection, the watts to amps calculator works differently. This is due to the fact that the power factor of the specified electrical device must also be considered.

As previously stated, our 50-watt lamp has a power factor of 1. In this situation, the calculation will be as follows, assuming the circuit voltage is 120 volts.

50 watts divided by the sum of the 1 PF multiplied by 120 volts equals 0.41 Amps.

  • For AC Three-Phase (Line to Line Voltage)

If your electrical system uses three-phase line-to-line voltage, you’ll need a slightly different formula to calculate the amps required for a 50-watt device. In that case, the formula will be as follows:

50 watts divided by the sum of √3 multiplied by 1 PF multiplied by 480 volts equals 0.060 amps.

  • For AC Three-Phase (Line to Neutral Voltage)

Finally, the calculation for the AC three-phase line-to-neutral voltage electrical connection will be as follows:

50 watts divided by the sum of 3 multiplied by 1 PF multiplied by 277 volts equals 0.060 amps. 

Factors Affecting Amps and Watts


1. Voltage

Voltage refers to the pressure of electric current through the circuit, and it can directly affect the watt and amp ratings. In general, increasing voltage means decreasing the current. At the same time, with the same current ratings, increasing voltage also increases power in terms of watts.

2. Power Factor

The power factor can affect the amp rating, since it converts electrical power into useful energy. A device with a low power factor will draw more current than one with a high-power factor, even if they have the same wattage.

3. Electrical Phases

The number of phases can also affect amps and watts, especially in three-phase circuits. This is because power is delivered over three wires. As a result, a device that runs in a three-phase system uses less current than a single-phase or DC electrical system, providing that the same voltage and wattage values are employed.

Frequently Asked Questions

How Many Amps Do 50 Watts Draw in a 220 Volt Circuit?

A 50 watts device, when used in a 220V circuit, can draw an average of 0.22 amps. However, this amp rating may change depending on the phases of the system used and the device’s power factor.

How Many Watts Can I Use in a Circuit?

The number of watts you can use in a circuit depends on the capacity of the circuit. However, most professionals suggest using only 1500 watts in an average household circuit.


Understanding how many amps is 50 watts is essential for the safety and efficiency of an electrical system. It can help you determine the number of device installations allowed in a circuit or whether you need to set up a new outlet.

Always remember that understanding the relationship between watts, amps, and voltage, as well as other factors affecting these values, can ensure that your electrical devices operate efficiently and safely.

Read more: Convert 12 watts to amp.

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